The present invention pertains to a miter box for making angled saw cuts in wooden boards and other workpieces and, more particularly, to a miter box having an improved device for holding a board in the box at an acute angle for making a compound angular cut and for locking the saw at a selected horizontal angle.
Miter boxes are well known and well developed in the prior art. The prior art discloses constructions which range from the very simple, including a true slotted box construction from which the name derives, to the very complex including sophisticated locating, alignment and clamping devices.
One problem relating to the use of a miter box which inventors have addressed for at least 100 years is the problem of properly positioning a board to be cut at an acute vertical angle from the horizontal miter box table when it is desired to make a compound angular cut. For example, when making a 45.degree. mitered saw cut in pieces of cove molding to be joined in the corner of a room, the molding piece must be positioned in the miter box at the same angle with respect to the horizontal table and vertical backstop that the molding will assume when affixed to the wall and ceiling. If properly positioned and cut, a mitered joint in a piece of ornamentally complex cove molding is much simpler to make than a contoured cut with a coping saw.
U.S. Pat. No. 497,524 shows an early attempt at providing means for positioning a board angularly with respect to the horizontal miter box table. The device utilizes adjustable holders on both the table and the vertical backstop, making its use rather complex. U.S. Pat. No. 761,817 shows a rack and pinion mechanism to provide adjustable angled board support. U.S. Pat. No. 976,296 shows the use of angular pans within which the board rests and which can be adjusted to vary the acute vertical angle at which the board is held for cutting.
U.S. Pat. No. 3,397,722 discloses a miter box in which horizontally adjustable stops in the supporting table may be set to position a piece of cove molding or picture frame molding at the necessary vertical angular position for making a compound angled miter cut. However, the apparatus is cumbersome to adjust and the stops protrude and interrupt the flat surface of the supporting table for normal use. U.S. Pat. Nos. 4,346,636 and 4,608,898 both show complex miter sawing apparatus which, among other things, provide special holding or fixturing means to angularly position a cove molding piece for making a compound angle mitered cut.
European Patent Application No. 92850278.0 discloses a very simple arrangement for making the compound angle mitered cuts described above. In this miter box, the horizontal supporting table is provided with a number of longitudinally extending grooves into which one edge corner of the board is positioned while the underside of the board adjacent the corner rests on the upper edge of the vertical backstop. The longitudinal grooves are parallel to one another and located at selected variable distances from the backstop corresponding to varying desired acute vertical angles at which the board must be disposed for cutting. However, the longitudinal grooves are relatively shallow and may provide adequate support only for a sharp square board corner. Furthermore, the grooves will provide no means of holding the corner on the back face of a cove molding strip because of the manner in which it is formed.
The prior art also discloses a wide variety of mechanisms for establishing and locking the saw in a selected horizontal position for making a mitered cut. Some miter boxes include positive locking stops between a protractor formed in the miter box table and a saw carriage which pivots on a vertical axis with respect to the protractor to select the desired horizontal angle. The locking stops are typically located at the position of commonly used horizontal angles, such as 45.degree., 60.degree., etc. Other miter boxes utilize frictional clamping means, such as a thumb screw to lock the saw carriage in any desired horizontal angular position. These devices, however, are often cumbersome to engage and disengage. U.S. Pat. No. 446,431 shows a simple wedge device utilized to lock a miter box saw guide in a selected horizontal angular position. However, little appears to have occurred in this century to adapt simple and easy to use horizontal angle locking techniques to modern miter box constructions.